The present invention is directed to gib assemblies of the type used typically in machine tool slide assemblies to maintain a slide surface in face-to-face contact with a guide rail surface by removing all clearance or looseness between the two sliding parts. In a typical gib installation, a guide slot is formed with a width greater than the width of a guide rail which is received within the slot. A pair of gib members are located between one side wall of the slot and the facing side wall of the guide rail. The two gib members are in face-to-face engagement with each other along a surface which is inclined to the side walls so that vertical movement of one gib element relative to the other exerts a wedging action which effectively narrows the width of the slot to produce a zero transverse clearance between the side walls of the slot, gib, and guide rail.
From the foregoing description, it is apparent that in order to take up or eliminate the clearance between the guide rail and the slot, adjustment of the position of one gib element relative to the other is required. This adjustment must be made in a manner such that all clearance is removed, but, at the same time, care must be taken that the adjustment is not made so tight as to interfere with free sliding movement between the rail and slot side wall. Typically, this adjustment involves a screw type adjustment of some sort, and typically the manual adjustment, once made, holds the two gib elements in fixed positions relative to each other. The initial setting is normally made with the parts stationary, a procedure which assumes the width of the slot and guide rail to be precisely uniform throughout their length as well as being precisely straight and parallel, conditions which do not always exist when the machine is operated under load.
The present invention is especially directed to a gib assembly which may be preset to establish a predetermined force of engagement between opposed sliding surfaces of a guide rail and slot and which is capable of automatically adjusting itself to compensate for variable conditions encountered during operation such as vibration, deflection under load, wear, etc.